This invention relates to overhead doors having torsion spring counterbalancing systems.
Overhead doors are widely used to close large openings in residential garages, commercial buildings, and industrial buildings. Overhead doors are made of multiple hinged panels with attached rollers that travel along tracks mounted on each side of the opening. Each track contains a vertical section adjacent the opening, an elevated horizontal section extending into the building, and a curved section connecting the vertical and horizontal sections. Some overhead doors are opened and closed manually while others contain powered operators. The doors are typically so heavy that a counterbalancing system is used to reduce the net downward force exerted by the door. Without the counterbalancing system, the force necessary to raise the door would exceed the capabilities of most persons and most powered operators.
Most counterbalancing systems contain either torsion springs or extension springs. A torsion spring is a helical spring that fits like a sleeve over a torsion bar mounted above the door. Cables are attached to the bottom of each side of the doors and then wound around drums on each end of the torsion bar. Extension springs are mounted horizontally along the horizontal section of the track. Torsion springs are generally preferred over extension springs for several reasons, including durability, noise, and smoothness of operation.
The most difficult and dangerous step in assembling a torsion spring counterbalancing system is the winding of the spring. The winding of a spring in a conventional system is illustrated in FIG. 1. A conventional counterbalancing system 10 includes a torsion bar 20, drums 30 and 31, a torsion spring 40, a stationary cone 50, and a winding cone 60. The stationary cone is attached to one end of the spring and the winding cone is attached to the other end. The stationary cone is secured to a bracket 70 which serves to anchor one end of the spring. Before winding the torsion spring, the rotation of the torsion bar must be restrained. In FIG. 1, rotation is restrained by fastening locking pliers onto the torsion bar. The pliers are then wedged against the header. The next step is to insert winding bars 100 and 101 into two of the four radial receptacles in the winding cone. The installer 110 (partially shown) then begins rotating the winding cone. With every quarter turn, a winding bar is removed and re-inserted into another receptacle. As the winding continues, a large amount of torque is created in the spring. When the spring is sufficiently wound (typically about seven rotations), the winding cone is secured to the torsion bar with set screws or the like. If for any reason during the winding process the installer loses his grip on the winding bars or if the winding bars slip out of the receptacles, the spring will rapidly unwind. The rapid unwinding can propel the winding bars outward and cause personal injury and property damage.
Winding of the torsion spring is frequently attempted by homeowners after installation. Over time, an adjustment of the torsion on the spring is often necessary. Typically, the spring needs to be wound slightly tighter to compensate for the slight loss in force due to repeated use. The winding operation is especially dangerous in this situation for two reasons. First, the homeowner is usually inexperienced. Second, when the torsion spring is originally wound, the installer begins the operation with an unwound spring and becomes familiar with the operation as the spring tension increases. In contrast, when the homeowner seeks to wind the spring tighter, the spring is already tightly wound. As a result, the homeowner is often unprepared to handle. the torque when the winding cone is loosened.
Alternative winding systems have been disclosed. For example, Mullet, U.S. Pat. No. 5,419,010, issued May 30, 1995, discloses a counterbalancing system in which the helical torsion spring is mounted inside the torsion bar. The spring is wound by using a conventional hex socket and electric drill to turn a worm gear. Carper et al., U.S. Pat. No. 5,632,063, issued May 27, 1997, also discloses a counterbalancing system in which the torsion spring is wound by using a tool to turn a worm gear. Such systems are relatively expensive, are not compatible with conventional components, and are difficult to install. Accordingly, a demand exists for a torsion spring counterbalancing system that is similar to conventional systems, but makes winding easier and safer.
The general object of this invention is to provide an improved torsion spring counterbalancing system for overhead doors. A more particular object is to provide a counterbalancing system that makes winding the torsion spring easier and safer by use of a ratcheting mechanism. Another more particular object is to provide a ratcheting counterbalancing system that is relatively inexpensive, compatible with conventional components, and is easy to install. Another more particular object is to provide an improved winding cone.
I have invented an improved ratcheting system for winding a helical torsion spring having a stationary end and a winding end around a torsion bar in a counterbalancing system for an overhead door having multiple panel sections. The ratcheting system comprises: (a) a cylindrical sleeve encompassing the torsion bar, the sleeve having longitudinal channels and being secured to the torsion bar at the winding end of the torsion spring; and (b) a winding cone adapted to fit over the cylindrical sleeve and having a cone-shaped section connected to the winding end of the torsion spring, a plurality of radial openings for receiving winding bars, a first threaded radial opening containing a set screw, and a second threaded radial opening containing a pull pin, the pull pin having a spring-biased beveled projection that extends inwardly from the winding cone to contact the longitudinal channels of the cylindrical sleeve. When the winding cone is rotated in a first direction with the bevel of the projection leading, the beveled projection passes over the longitudinal channels and when the winding cone is rotated in the opposite direction with the bevel of the projection trailing, the beveled projection engages the longitudinal channel and prevents further rotation.
This ratcheting system is compatible with conventional components and serves as a replacement for the conventional winding cone. It is relatively inexpensive and is easy to install. The ratcheting mechanism ensures the torsion spring will not unwind unless desired. It therefore makes the winding of the torsion spring much easier and safer.